[Ffmpeg-devel] mpeg2 muxer: lpcm issue

Chris chris
Wed Aug 2 17:10:06 CEST 2006

M?ns said:

>>I'll have a look as soon as I  have access to something with a little more
power than a Nokia 770.


I have been looking at this and come up with the following information which
may help you with any investigation:

Firstly I ran the output mpeg through Phillips DVD-Video verifier which
spewed out many DVD/Mpeg issues but a few were interesting to this

First: [DVD] ERROR 3235  (ref. DVD-3 Fig. 5.2.3/4/5-1)


Search for "ERROR 3235"

This error would indicate that the max payload for LPCM PES packets is 2017
where as the output mpeg has 2019...

Also: [DVD] ERROR 3870  (ref. DVD-3 Table 5.2.4-1, note 3) :
    The number_of_frame_headers (7) must describe the number of audio frames
	whose first byte is in this A_PKT

And: [DVD] ERROR 3871:
	The first_access_unit_pointer (value 4) must describe the address
	of the first byte of the first AU in this A_PCK

The first "error" can be sorted by reducing the payload_size and adjusting
the stuffing. The last two issues pointed me to investigate the audio
substream headers in dvd's (please see attached - if it comes through!).

The issue here is that the first 3 bytes of the header (frame count, and
offset to first access unit) are always the same in mpeg.c yet I assume they
need to be dynamic. Also FrmNum in the fourth byte should be dynamic too.

It is unclear to me whether these are purely DVD Vob issues or mpeg 2
program stream issues too.

Hope this helps.


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